Does anyone have any recomendations how to synchronize (3) Tetrix motors, with encoders, in the same PID loop?

Wed Jan 23, 2013 10:45 pm

JohnWatson

Site Admin

Joined: Thu May 24, 2012 12:15 pmPosts: 672

Re: 3 tetrix motors in the same PID loop

Unfortunately, it is not currently possible for ROBOTC to synch TETRIX motors together; for more information on why this is not possible, please see this thread. You could, however, possibly write a custom PID control program that would essentially synchronize the motors.

You can write simple PID control yourself to do it. However, if latency is an issue with Tetrix motors, it may not address the issue. But in theory, if you have your own PID control, you probably can tune your PID constants such that the system doesn't oscillate. If the system doesn't oscillate, the latency is less of an issue.

Thu Jan 24, 2013 1:30 pm

tom.jakowenko

Rookie

Joined: Wed Jan 23, 2013 6:16 pmPosts: 7

Re: 3 tetrix motors in the same PID loop

A basic position loop comes to mind where the position of each motor is compared and the difference between them (error) is used to increase/decrease power to the others. I'm thinking it would be best to declare one of them as a master and other two as slaves. The only exception would be if the correction power exceeds 100%, in which case I would have to slow down the master.

Does this sound like a reasonable approach?

Can you recommend a good resource to provide some PID background?

Thu Jan 24, 2013 1:52 pm

MHTS

Guru

Joined: Sun Nov 15, 2009 5:46 amPosts: 1512

Re: 3 tetrix motors in the same PID loop

Just google PID control. Wikipedia has a pretty good description of it.

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